1. Field of the Invention
This invention relates to projectiles for liquid propellant guns. More particularly, this invention relates to projectiles containing shock buffers.
2. Description of the Prior Art
Experimentation is presently being carried out in efforts to develop a liquid propellant gun suitable for military use. A liquid propellant gun is one in which gases produced by ignited propellant are used to drive a projectile from the barrel. The use of a liquid propellant in lieu of the conventional material, gun powder, offers many potential advantages among which is the advantage of eliminating the need for cartridge cases.
A liquid propellant gun contains, among other parts, a barrel and a firing chamber. During the loading cycle, a projectile is, at one point in time, at the rear of the firing chamber. At this point in time, liquid propellant is injected behind the projectile and a bolt is used to force the liquid and the projectile in front of it forward until the projectile seats in the rear of the barrel and the liquid fills the firing chamber behind the projectile. At this point in time, i.e., when the projectile is seated in the rear of the barrel and the liquid fills the firing chamber, the rear of the firing chamber is closed by the bolt. The gun is now ready for firing. To fire, a spark mechanism in the firing chamber is activated. The spark ignites the liquid propellant and hot expanding gases produced by the propellant drive the projectile out through the barrel.
In the past, the projectile has typically been a solid metallic projectile. It has typically, although not necessarily, been coated, on its rear portions, with a thin layer of Viton A or the like. The thin coating of Viton A or the like has been utilized to prevent liquid propellant from flowing forward, around the periphery of the projectile, into the gun barrel as the projectile seats in the rear of the barrel.
When the propellant in a liquid propellant gun is ignited, tremendous pressure rises occur in the firing chamber. A shock wave travels through the liquid, strikes the base of the projectile and is reflected back. This reflected wave amplifies, up to 90%, the normal pressure in the firing chamber and sometimes causes expansion and damage to the firing chamber. Pressures of up to 150,000 psi have been measured in the firing chamber.
Because of these tremendous pressures, the chamber has previously been required to be very thick-walled. The wall of the cylindrical chamber in a typical gun has been on the order of 11/4 inches thick and the chambers have typically been made of high strength stainless steel. Because of this required thickness of the chamber wall, the firing chamber has naturally been a very heavy part of the gun. Because weight considerations are of great importance when any article is to be incorporated as part of an aircraft, it would be desirable to be able to reduce the thickness of the wall of the firing chamber and thus make the part lighter.